Exhaust purification system for working machine

ABSTRACT

An exhaust purification system for a working machine reliably issues filter regeneration warnings to the operator, prompting manual regeneration, so that damage to the DPF device can be avoided. When a PM estimate becomes higher than a given value, a screen displays a warning message prompting manual regeneration. If the warning message fails to prompt the operator to perform manual regeneration and reference time t 1  has passed since the display of the warning message, a speaker outputs a first warning sound. When the operator notices the first warning sound and turns on a regeneration switch, regeneration control is started. If the operator fails to notice the first warning sound and reference time t 2  passes, the speaker instead outputs a second warning sound louder than the first warning sound. When the operator notices the second warning sound and turns on the regeneration switch, regeneration control is started.

TECHNICAL FIELD

The present invention relates to exhaust purification systems forworking machine and particularly to an exhaust purification system thatuses a filter to capture the particulate matter contained in exhaust forpurifying the exhaust and prompts the operator to start manual filterregeneration so that the particulate matter captured by the filter canbe burnt off and removed.

BACKGROUND ART

Working machine (e.g., hydraulic excavators) has a diesel engine as itspower source. The particulate matter (PM) discharged from the dieselengine and other hazardous substances such as NOx, CO, and HC aresubject to severer emission regulations year by year. Such being thecase, there exists an exhaust purification system that uses a dieselparticulate filter (DPF) to capture particulate matter, thereby reducingPM emission. Such a system burns the particulate matter captured by thefilter to prevent its clogging, thereby regenerating the filter.Otherwise, an increase in the PM accumulated on the filter may clog thefilter, which increases the exhaust temperature of the engine anddeteriorates fuel efficiency.

Filter regeneration is often performed with the use of an oxidationcatalyst. The catalyst is positioned upstream of the filter or directlysupported by the filter or both. In either case, activating the catalystrequires exhaust temperature to be higher than the activationtemperature of the catalyst. When exhaust temperature is sufficientlyhigh, the filter self-regenerates, but there are also cases whereexhaust temperature is too low for self-regeneration and whereself-regeneration is not enough for burning particulate matter. In suchcases, compulsory regeneration is employed to raise exhaust temperatureabove the activation temperature of the catalyst. Methods of compulsoryregeneration include one in which fuel injection is performed during theexpansion stroke after main fuel injection into the engine cylinder; onein which fuel is injected into the exhaust gas within the exhaust pipewith the use of a fuel injector disposed within the exhaust pipe; one inwhich the engine load is increased by raising the engine speed; and onein which the engine load is increased by utilizing the hydraulic loadeffect.

Compulsory filter regeneration also includes automatic regeneration inwhich regeneration is started automatically and manual regeneration inwhich regeneration is started by the operator. Automatic regeneration isperformed when an estimated amount of accumulated PM reaches a thresholdor when a given amount of time has passed. If automatic regeneration isnot performed properly, the accumulation of particulate matter mayproceed.

Patent Document 1 discloses a technique related to manual regenerationin which a warning is issued to the operator (e.g., via a warning lamp)to prompt manual regeneration. When the operator turns on theregeneration switch, regeneration is started.

During the excavation work by a hydraulic excavator, the operator mayfail to notice a warning prompting manual regeneration if he is toofocused on the work. Moreover, if he places high priority on thecompletion of the work, he may ignore the manual regeneration warning.If manual regeneration is not performed after the warning, theaccumulation of PM will proceed. Eventually, the in-filter temperaturemay increase excessively due to the combustion of a large amount of PM,damaging the DPF device.

In the technique of Patent Document 1, the form of a warning is changedbased on an estimated amount of accumulated PM. At first, a warning lampflashes slowly, but when the DPF device is more likely to be damaged dueto an increased amount of PM, the warning lamp starts to flash quickly.While the technique of Patent Document 1 is related to automobiles ingeneral, it is also applicable to working machine such as hydraulicexcavators. With the technique of Patent Document 1, the operator canrecognize the urgency of the necessity of manual regeneration bynoticing warning changes. By the operator then performing manualregeneration properly, damage to the DPF device can be avoided.

PRIOR ART LITERATURE Patent Document

Patent Document 1: JP,A 2005-299403

SUMMARY OF THE INVENTION Problem to be Solved by the Invention

In filter regeneration, whether automatic or manual, the amount ofaccumulated PM is often estimated by detecting the differential pressureacross the filter and then performing calculations based on thedifferential pressure. Thus, the accuracy of control based on anestimated amount of accumulated PM depends on the accuracy of that PMestimate. In other words, when the PM estimate has errors, warningscannot be changed properly. When a PM estimate is higher than the actualPM amount and warnings are changed based on that estimate, the errorcauses no problems. However, when a PM estimate is lower than the actualPM amount and warnings are changed based on that estimate, judgmentassociated with the alteration of the warnings may be delayed. Thisdelay could be an indirect cause of DPF breakage because manualregeneration cannot be performed properly (i.e., the start of the manualregeneration is delayed).

An object of the present invention is to provide an exhaust purificationsystem for working machine that reliably issues filter regenerationwarnings to the operator, prompting manual regeneration, so that damageto the DPF device can be avoided.

Means for Solving the Problem

(1) To achieve the above object, the present invention provides anexhaust purification system for working machine, the system comprising:a filter, located in an exhaust system of an engine, for capturingparticulate matter contained in exhaust; a regeneration device forburning off particulate matter accumulated on the filter to regeneratethe filter; a regeneration controller for starting or stopping theoperation of the regeneration device; a regeneration switch forinstructing the regeneration controller to start regeneration; andwarning means for prompting an operator to turn on the regenerationswitch. The system further comprises status judging means for judgingthe status of the working machine, and the warning means includes awarning altering function for altering the content of warnings based onthe amount of time during which the status judging means judges theworking machine to be in operation since a first warning.

(2) To achieve the above object, the invention also provides an exhaustpurification system for working machine, the system comprising: afilter, located in an exhaust system of an engine, for capturingparticulate matter contained in exhaust; a regeneration device forburning off particulate matter accumulated on the filter to regeneratethe filter; a regeneration controller for starting or stopping theoperation of the regeneration device; a regeneration switch forinstructing the regeneration controller to start regeneration; andwarning means for prompting an operator to turn on the regenerationswitch. The system further comprises status judging means for judgingthe status of the working machine, and the warning means includes awarning sound output function for outputting warning sounds and awarning sound altering function for altering the warning sounds when theamount of time during which the status judging means judges the workingmachine to be in operation exceeded reference times after a firstwarning.

In conventional techniques, the content of a warning is changed based onan estimated amount of accumulated PM. Thus, if the estimate has errors,the warning may not be changed properly. In contrast, changing warningsounds based on elapsed time as above allows the warning sounds to bechanged more reliably without being affected by PM estimation errors,and by the operator noticing the warning sounds and performing manualregeneration, damage to the DPF device can be avoided.

(3) In the above system of (2), in the event that the status judgingmeans judges the working machine to be in operation, the status judgingmeans further judges whether the working machine is in standby status orwork-in-progress status and wherein the warning sound altering functionsets different reference times depending on the standby status or thework-in-progress status.

During standby status, more particulate matter may be accumulated thanduring work-in-progress status. Thus, during standby status, changingwarning sounds based on the reference times for work-in-progress statusmay delay judgment associated with the alteration of the warning sounds.Therefore, during standby status, warning sounds are changed based onthe reference times for standby status, thereby preventing the judgmentfrom being delayed and ensuring a reliable alternation of warningsounds.

(4) In the above system of (3), the working machine comprises: an enginespeed detector; a work-performing structure; operating levers forcontrolling the operation of the work-performing structure; a gate locklever movable between an unlock position that enables the operation ofthe operating levers and a lock position that disables the operation ofthe operating levers; and a pilot pressure sensor for detecting pilotpressures generated by the operating levers. The status judging meansjudges the working machine to be in the standby status in the event thatthe engine speed detector has detected a speed higher than a low idlespeed and that the gate lock lever is in the lock position. On the otherhand, the status judging means judges the working machine to be in thework-in-progress status in the event that the engine speed detector hasdetected a speed higher than the low idle speed, that the gate locklever is in the unlock position, and that the pilot pressure sensor hasdetected a pressure higher than a given value.

The above allows the warning sound altering function to change warningsounds based on the reference times for work-in-progress status duringwork-in-progress status and based on the reference times for standbystatus during standby status.

(5) In the above system of (2), the warning sound altering functionalters at least either one of the following: the volume, tone, length,and repeat count of the warning sounds.

With such alteration of the warning sounds, it becomes more likely forthe operator to notice the sounds.

(6) To achieve the above object, the invention further provides anexhaust purification system for working machine, the system comprising:a filter, located in an exhaust system of an engine, for capturingparticulate matter contained in exhaust; PM estimating means forestimating the amount of particulate matter accumulated on the filter; aregeneration device for burning off the particulate matter accumulatedon the filter to regenerate the filter; a regeneration controller forstarting or stopping the operation of the regeneration device; aregeneration switch for instructing the regeneration controller to startregeneration; and warning means for prompting an operator to turn on theregeneration switch. The warning means includes a warning sound outputfunction for outputting warning sounds and a warning sound alteringfunction for altering the warning sounds based on the PM amountestimated by the PM estimating means.

EFFECT OF THE INVENTION

In accordance with the invention, filter regeneration warnings can beissued to the operator in a more reliable manner, and with proper manualregeneration, damage to the DPF device can be avoided.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates the overall configuration of an exhaust purificationsystem according to Embodiment 1;

FIG. 2 illustrates the hydraulic circuit employed in a hydraulicexcavator;

FIG. 3 is an external view of the hydraulic excavator;

FIG. 4 illustrates the functional blocks of a controller;

FIG. 5 is a flowchart illustrating the calculations performed by thecontroller;

FIG. 6 illustrates a problem associated with Embodiment 1; and

FIG. 7 illustrates an advantage of Embodiment 2.

MODE FOR CARRYING OUT THE INVENTION Embodiment 1

Embodiment 1 of the present invention will now be described withreference to the accompanying drawings.

Configuration

FIG. 1 illustrates the overall configuration of an exhaust purificationsystem for working machine according to Embodiment 1.

The working machine of FIG. 1 (a hydraulic excavator being shown as anexample) has a diesel engine 1 installed. The diesel engine 1 includesan electronic governor 1 a, an electronic device for controlling fuelinjection. A target speed of the engine 1 is set by an engine controldial 2, and the actual speed of the engine 1 is detected by a speeddetector 3. A controller 4 receives a command signal from the enginecontrol dial 2 and a speed signal from the speed detector 3 and controlsthe electronic governor la based on the command signal (indicative ofthe target speed) and the speed signal (indicative of the actual speed),thereby controlling the speed and torque of the engine 1.

A key switch 5 is used to start or stop the engine 1. The controller 4also receives a command signal from the key switch 5 and controls thestart and stop of the engine 1 based on that signal. The key switch 5also acts as a device for starting or stopping power supply for thecontroller 4 and a display device 6.

Operating levers 28 and 29 (see FIG. 2) and a gate lock lever 7 areinstalled within the cab 107 of the hydraulic excavator. The gate locklever 7 can be moved between position A (unlock position) that closesthe entrance to a cab seat 108 and position B (lock position) that opensthe entrance to the cab seat 108. The gate lock lever 7 includes aposition detector 8 for detecting the position of the lever 7.

The exhaust purification system is installed on the exhaust pipe 31 ofthe engine 1. The system includes the following components: a DPF device34 including a filter 32 for capturing the particulate matter containedin exhaust and an oxidation catalyst 33 located upstream of the filter32; a differential pressure detector 36 for detecting the differentialpressure across the filter 32 (i.e., pressure loss across the filter32); an exhaust temperature detector 37, located upstream of the filter32, for detecting exhaust temperature; a regeneration switch 38 forstarting filter regeneration; and a fuel injector 39, located within theexhaust pipe 31 (i.e., between the engine 1 and the DPF device 34), forincreasing the exhaust temperature. The oxidation catalyst 33 and thefuel injector 39 constitute a filter regeneration device that burns offthe particulate matter accumulated on the filter 32.

The regeneration switch 38 is located at an easily accessible positionwithin the cab 107 of the hydraulic excavator. The operator uses theregeneration switch 38 to start the regeneration of the filter 32. Whenturned on, the regeneration switch 38 outputs a command signal thatstarts the regeneration of the filter 32. The regeneration switch 38 mayinstead be an icon displayed on the display device 6. In either case,the regeneration switch is operated for the operator to turn it on oroff.

The display device 6 is located at an easily viewable position withinthe cab 107 of the hydraulic excavator and designed to show basicvehicle information such as remaining fuel, coolant temperature, and soon. The display device 6 includes a screen 6 a, control switches 6 b,and a speaker 6 c, and its operation is controlled by the displaycontroller 43 (see FIG. 4) of the controller 4. The control switches 6 bare located below the screen 6 a. By the operator operating the switches6 b, the screen 6 a can display information other than the basic vehicleinformation. The screen 6 a and the control switches 6 b serve as aninterface, allowing the operator to operate the switches 6 b whileviewing the screen 6 a for changing various vehicle-related settings.

The display device 6 also displays regeneration-related information suchas the status of automatic regeneration, a warning prompting theoperation of the regeneration switch 38, and so forth. The speaker 6 ccan output such information in the form of voice.

In the present embodiment, the speaker 6 c outputs warning sounds whenmanual regeneration is not being done properly (described later indetail).

FIG. 2 illustrates the hydraulic circuit employed in the constructionmachine (e.g., hydraulic excavator). The hydraulic circuit includes thefollowing components: a variable-displacement hydraulic pump 11 (i.e.,main pump) and a fixed-displacement pilot pump 12 both driven by theengine 1; a hydraulic motor 13 and hydraulic cylinders 14 and 15 (i.e.,hydraulic actuators) driven by the hydraulic fluid discharged from thehydraulic pump 11; pilot flow-rate control valves 17 to 19 forcontrolling the flow (i.e., flow rate and direction) of the hydraulicfluid fed from the hydraulic pump 11 to the hydraulic motor 13 and thehydraulic cylinders 14 and 15; a pilot relief valve 21 for maintainingthe pressure of the hydraulic fluid discharged from the pilot pump 12 ata constant value (the pilot relief valve 21 constituting a pilothydraulic pressure source 20); a main relief valve 22 for determining anupper limit to the discharge pressure of the hydraulic pump 11; asolenoid valve 23 connected to the downstream side of the pilothydraulic pressure source 20 and turned on or off depending on theposition of the gate lock lever 7 located at the entrance to the cabseat; and remote control valves 25, 26, and 27, connected to a pilothydraulic line 24 located downstream of the solenoid valve 23, forgenerating, based on the hydraulic pressure of the pilot hydraulicpressure source 20, control pilot pressures a to f to control theflow-rate control valves 17 to 19.

The hydraulic pump 11 includes a regulator 11 a for controlling the tiltof the hydraulic pump 11 (i.e., the tilt of the swash plate, hence thedisplacement volume of the pump 11) based on the discharge pressure ofthe pump 11 so that the absorption torque (consumption torque) of thepump 11 will not exceed a given maximum absorption torque.

The remote control valves 25, 26, and 27 are controlled by the operatinglevers 28 and 29 installed at the right and left sides of the cab seat108 (see FIG. 1). The operating levers 28 and 29 can be moved crosswise.Moving the operating lever 28 in the directions of one line of a crossoperates the remote control valve 25 while moving the operating lever 28in the directions of the other line of the cross operates the remotecontrol valve 27. Likewise, moving the operating lever 29 in thedirections of one line of a cross operates the remote control valve 26while moving the operating lever 29 in the directions of the other lineof the cross operates another remote control valve not illustrated. Whenthe operating lever 28 is moved in the two directions of one line of across, moving the lever 28 in one of the two directions from its neutralposition causes the remote control valve 25 to generate the controlpilot pressure a while moving the lever 28 in the other direction causesthe remote control valve 25 to generate the control pilot pressure b.The control pilot pressures a and b are directed to the associatedpressure receivers of the flow-rate control valve 17 through pilot lines25 a and 26 b, thereby moving the flow-rate control valve 17 from itsneutral position.

Similarly, when the operating lever 28 is moved in the two directions ofthe other line of the cross, moving the lever 28 in one of the twodirections from the neutral position causes the remote control valve 27to generate the control pilot pressure e while moving the lever 28 inthe other direction causes the remote control valve 27 to generate thecontrol pilot pressure f. The control pilot pressures e and f aredirected to the associated pressure receivers of the flow-rate controlvalve 19 through pilot lines 27 a and 27 b, thereby moving the flow-ratecontrol valve 19 from its neutral position. Likewise, when the operatinglever 29 is moved in the two directions of one line of a cross, movingthe lever 29 in one of the two directions from its neutral positiongenerates the control pilot pressure c while moving the lever 29 in theother direction generates the control pilot pressure d. The controlpilot pressures c and d are directed to the associated pressurereceivers of the flow-rate control valve 18 through pilot lines 26 a and26 b, thereby moving the flow-rate control valve 18 from its neutralposition.

The hydraulic circuit further includes shuttle valves 46 and a pressuresensor 47. The shuttle valves 46 are designed to extract the highestpressure among the control pilot pressures a to f of the remote controlvalves 26 to 27 and the control pilot pressures of other operatingunits. The pressure sensor 47 is connected to the output port of theshuttle valve 46 located furthest downstream and used to detect thehighest control pilot pressure to detect the operation of an operatinglever or unit.

The control pilot pressures a to f are allowed to flow or blockeddepending on the position of the gate lock lever 7.

When the gate lock lever 7 is placed in position A (see FIG. 1), thesolenoid of the solenoid valve 23 is excited, shifting the solenoidvalve 23 from the position of FIG. 2 and directing the hydraulicpressure of the pilot hydraulic pressure source 20 to the remote controlvalves 25, 26, and 27. This allows the remote control valves 25, 26, and27 to control the flow-rate control valves 17 to 19. When the gate locklever 7 is raised to position B (see FIG. 1), the solenoid of thesolenoid valve 23 becomes inactive, shifting the solenoid valve 23 tothe position of FIG. 2 and disconnecting the pilot hydraulic pressuresource 20 from the remote control valves 25, 26, and 27. This preventsthe remote control valves 25, 26, and 27 from controlling the flow-ratecontrol valves 17 to 19. In other words, when the gate lock lever 7 isin position B, the remote control valves 25, 26, and 27 (control leverunits) are locked, and lowering the gate lock lever 7 to position Aunlocks the valves 25, 26, and 27. Shifting the position of the solenoidvalve 23 by the gate lock lever 7 can be achieved by, for example,installing a switch between the solenoid of the solenoid valve 23 andits power source. When the gate lock lever 7 is in position A, thatswitch is turned on (closed state) to excite the solenoid. When the gatelock lever 7 is in position B, the switch is turn off (open state) tomake the solenoid inactive.

FIG. 3 is an external view of the hydraulic excavator. The excavatorincludes a lower carrier structure 100, an upper swing structure 101,and a front shovel structure 102. The lower carrier structure 100includes crawler belts 103 a and 103 b driven by travel motors 104 a and104 b, respectively. The upper swing structure 101 is mounted on thelower structure 100 in a swingable manner via a swing motor 105. Thefront shovel structure 102 is attached to the front end of the upperstructure 101 in a vertically rotatable manner. The upper swingstructure 101 has an engine room 106 and the cab 107 mounted thereon.The engine 1 is installed within the engine room 106, and the gate locklever 7 (see FIG. 1) is installed at the entrance to the cab seat 108 ofthe cab 107. Installed at the left and right sides of the cab seat 108are the control lever units housing the remote control valves 25, 26,and 27 (see FIG. 2).

The front shovel structure 102 is a multi-joint structure including aboom 111, an arm 112, and a bucket 113. The boom 111 is rotatedvertically by the expansion and contraction of a boom cylinder 114. Thearm 112 is rotated upward or downward and forward or backward by theexpansion and contraction of an arm cylinder 115. The bucket 113 isrotated upward or downward and forward or backward by the expansion andcontraction of a bucket cylinder 116.

The hydraulic motor 13 and hydraulic cylinders 14 and 15 of FIG. 2 couldbe, for example, the swing motor 105, the arm cylinder 115, and the boomcylinder 114, respectively. While the hydraulic drive system of FIG. 2further includes other hydraulic actuators and control valves for themotors 104 a and 104 b, the bucket cylinder 116, and the like, FIG. 2does not illustrate such components.

It should be noted that the working machine to which the invention isapplied may instead be a wheel loader or a wheel-mounted hydraulicexcavator.

Control

FIG. 4 illustrates the functional blocks of the controller 4. Thecontroller 4 includes a vehicle controller 41, an engine controller 42,and a display controller 43. These controllers are mutually connectedvia a communication line 44, forming a vehicle network. The vehiclecontroller 41 receives command signals from the engine control dial 2,detection signals from the position detector 8 and the pressure sensor47, and command signals from the regeneration switch 38 while the enginecontroller 42 receives detection signals from the speed detector 3, thedifferential pressure detector 36, and the exhaust temperature detector37.

The vehicle controller 41 is designed to control overall vehicleoperation including the hydraulic drive system. For instance, thevehicle controller 41 controls the regulator 11 a of the hydraulic pump11, thereby controlling the discharge pressure and discharge flow-rateof the pump 11. The vehicle controller 11 also performs switch controlof the solenoid valve 23 for gate locking.

The engine controller 42 receives a command signal from the enginecontrol dial 2 through the communication line 44. The engine controller42 uses this command signal and a signal from the speed detector 3 tocontrol the speed and torque of the engine 1.

The engine controller 42 also receives a signal from the differentialpressure detector 36 to estimate the amount of accumulated particulatematter and performs calculations for regeneration control based on theestimate. Based on the calculations, the engine controller 42 thencontrols the electronic governor la and the fuel injector 39 (automaticregeneration control).

The display controller 43 receives various signals and the calculationsresults through the communication line 44 and transmits display signalsto the display device 6 so that such information can be displayed on thescreen 6 a. If necessary, voice signals are transmitted to the speaker 6c. The display controller 43 also allows the input of command signalsfrom the control switches 6 b, part of the user interface.

The engine controller 42 includes a manual regeneration function 42 a.The manual regeneration function 42 a receives a signal from thedifferential pressure detector 36 to estimate the amount of accumulatedparticulate matter and transmits a warning signal to the displaycontroller 43 based on the estimation. The manual regeneration function42 a further receives a command signal from the regeneration switch 38via the communication line 44 and then controls the electronic governorla and the fuel injector 39 (manual regeneration control).

A feature of the present embodiment is that the vehicle controller 41includes a status judgment function 41 a, a warning sound alteringfunction 41 b, and a memory 41 c.

The status judgment function 41 a judges the status of the hydraulicexcavator (whether it is in operation or not). When it is in operation,the status judgment function 41 a further judges whether it is in astandby status or work-in-progress status.

The status judgment function 41 a receives a signal from the speeddetector 3 through the communication line 44. When the actual enginespeed exceeds a low idle speed, the status judgment function 41 a judgesthe excavator to be in operation. When, on the other hand, the actualengine speed is less than the low idle speed, the status judgmentfunction 41 a judges the excavator not to be in operation.

When the excavator is judged to be in operation, the status judgmentfunction 41 a receives signals from the position detector 8 and thepressure sensor 47. When the gate lock lever 7 is in the lock position,the status judgment function 41 a judges the excavator to be in astandby status. When, on the other hand, the gate lock lever 7 is in theunlock position and the pilot pressure exceeds a given value, theexcavator is judged to be in a work-in-progress status.

The warning sound altering function 41 b sets reference times t1, t2,and t3 (t1<t2<t3) based on the judgment results obtained by the statusjudgment function 41 a. When the results reveal that the excavator is ina standby status, the warning sound altering function 41 b readsreference times for standby status from the memory 41 c. When theresults reveal that the excavator is in a work-in-progress status, thewarning sound altering function 41 b reads reference times forwork-in-progress status from the memory 41 c. The reference times t1,t2, and t3 for standby status are shorter than the reference times t1,t2, and t3 for work-in-progress status, respectively.

After receiving a warning signal from the manual regeneration function42 a, the warning sound altering function 41 b starts time measurementfrom that point of time.

When the elapsed time exceeds the reference time t1 for standby status(or for work-in-progress status), the warning sound altering function 41b reads the voice data of a first warning sound from the memory 41 c andoutputs the data to the display controller 43 in the form of a voicesignal. When the elapsed time exceeds the reference time t2 for standbystatus (or for work-in-progress status), the warning sound alteringfunction 41 b then reads the voice data of a second warning sound fromthe memory 41 c and outputs the data to the display controller 43 in theform of a voice signal. When the elapsed time exceeds the reference timet3 for standby status (or for work-in-progress status), then, thewarning sound altering function 41 b reads the voice data of a thirdwarning sound from the memory 41 c and outputs the data to the displaycontroller 43 in the form of a voice signal.

FIG. 5 is a flowchart illustrating the calculations performed by thecontroller 4.

We describe the manual regeneration control first. Note that while themanual regeneration control is performed in parallel with the automaticregeneration control, we describe only the former control forsimplification purposes.

The controller 4 first judges whether or not the amount of particulatematter estimated based on a signal from the differential pressuredetector 36 is greater than a first threshold, a value indicative of thenecessity of manual regeneration (Step S11). If not, Step S11 isrepeated until the estimated amount becomes greater than the firstthreshold.

After judging the estimated amount to be greater than the firstthreshold in Step S11, the controller 4 outputs a warning signal toprompt the operator to turn on the regeneration switch 38. This causesthe screen 6 a to display a warning prompting manual regeneration (StepS12).

The controller 4 then judges whether the regeneration switch 38 has beenturned on or not (Step S13). If not, the warning continues to bedisplayed until the regeneration switch 38 is turned on. During thattime, the controller 4 also performs warning sound control (describedlater in detail).

After judging the regeneration switch 38 to be turned on in Step S13,the controller 4 starts manual regeneration control (Step S13).

The regeneration control can be performed in the following manner. Thespeed of the engine 1 is first controlled to a given speed Na suitablefor compulsory regeneration control. The given speed Na is a middlespeed that makes exhaust temperature higher than the activationtemperature of the oxidation catalyst 33. In this control, the vehiclecontroller 41 changes the target speed of the engine 1 from the targetspeed specified by the engine control dial 2 to the given speed Na andoutputs the given speed Na to the engine controller 42 via thecommunication line 44. The engine controller 42 then performs feedbackcontrol on the fuel injection amount of the electronic governor la basedon the given speed Na and the actual engine speed detected by the speeddetector 3, thereby controlling the speed of the engine 1 to the givenspeed Na.

After the exhaust temperature detected by the exhaust temperaturedetector 37 increases up to a given value (a temperature higher than theactivation temperature of the oxidation catalyst 33), the controller 4then instructs the fuel injector 39 to inject fuel into the exhaust pipe31. This allows unburnt fuel components to be supplied to and oxidizedby the catalyst 33. The reaction heat obtained from the oxidationincreases the exhaust temperature further, burning off the particulatematter accumulated on the filter 32. The exhaust temperature may insteadbe raised by increasing the engine load by increasing the engine speedor utilizing the hydraulic load effect.

During the regeneration control, the controller 4 judges whether or notthe estimated amount of particulate matter is less than a secondthreshold, a value with which to judge the completion of theregeneration (Step S15). If so, the manual regeneration control isterminated (Step S16). If not, the regeneration control is continueduntil the estimated amount becomes less than the second threshold.

When the regeneration control is terminated, the target engine speed isset back to the target speed specified by the engine control dial 2(i.e., low idle speed), and the operation of the fuel injector 39 isstopped. Alternatively, it is also possible to halt the engine 1 inplace of setting the target engine speed back to the target speedspecified by the engine control dial 2 (i.e., low idle speed).

Described next is warning sound control.

The status of the hydraulic excavator is judged in advance (Step S21).Based on the results (whether the excavator is in a standby status orwork-in-progress status), the controller 4 sets the reference times t1,t2, and t3 for standby status or for work-in-progress status (Step S22).

After a warning is displayed to prompt manual regeneration in Step S12,the controller 4 starts time measurement from that point of time (StepS23).

The controller 4 first judges whether the elapsed time has exceeded thereference time t1 (Step S24). If not, Steps S13 and S24 are repeateduntil the regeneration switch 38 is turned on or until the elapsed timeexceeds the reference time t1. When the elapsed time exceeds thereference time t1, the controller 4 outputs a first warning sound (StepS25).

The controller 4 then judges whether the elapsed time has exceeded thereference time t2 (Step S26). If not, Steps S13, S24, and S25 arerepeated until the regeneration switch 38 is turned on or until theelapsed time exceeds the reference time t2, thus continuing the outputof the first warning sound. When the elapsed time exceeds the referencetime t2, a second warning sound is output in place of the first warningsound (Step S27).

The controller 4 further judges whether the elapsed time has exceededthe reference time t3 (Step S28). If not, Steps S13 and S24 to S27 arerepeated until the regeneration switch 38 is turned on or until theelapsed time exceeds the reference time t3, thus continuing the outputof the second warning sound. When the elapsed time exceeds the referencetime t3, a third warning sound is output in place of the second warningsound (Step S29).

After judging the regeneration switch 38 to be turned on in Step S13,the controller 4 starts manual regeneration control (Step S13). If, onthe other hand, a particular amount of time has passed since the outputof the third warning sound and regeneration has not been started yet,the controller 4 prohibits the regeneration (not illustrated). This isbecause an excessive amount of accumulated particulate matter may burnabruptly, increasing the filter temperature excessively and damaging thefilter.

Terms Used in Claims

Step S12 performed by the manual regeneration function 42 a, the displaycontroller 43, and the screen 6 a of the present embodiment constitute“warning means” for prompting the operation of the regeneration switch38.

The speed detector 3, the position detector 8, the pressure sensor 47,and Step S21 performed by the status judgment function 41 a constitute“status judging means” for judging the status of working machine.

Steps S23 to S29 performed by the warning sound altering function 41 bconstitute “warning sound altering function” for altering warning soundswhen the amount of time during which the working machine is being judgedto be in operation exceeded reference times after the display of awarning prompting manual regeneration.

Operation

(1) Now described is the basic operation of the exhaust purificationsystem of Embodiment 1.

While the excavator is in operation, automatic regeneration control isperformed. However, the accumulation of particulate matter proceeds ifthe automatic regeneration control is not performed properly for somereason. When the accumulated PM amount becomes higher than a firstthreshold, a warning message is displayed on the screen 6 a to promptmanual regeneration. Regeneration control is started by the operatorturning on the regeneration switch 38. After the accumulated PM is burntand the accumulated PM amount becomes smaller than a second threshold,the regeneration control is stopped (the process flows from S11 to S12,to S13, to S14, to S15, and to S16).

During the excavation work by the hydraulic excavator, the operator mayfail to notice a warning prompting manual regeneration if he is toofocused on the work. Moreover, if he places high priority on thecompletion of the work, he may ignore the manual regeneration warning.If manual regeneration is not performed after the warning, theaccumulation of PM will proceed. Eventually, the in-filter temperaturemay increase excessively due to the combustion of a large amount of PM,damaging the DPF device.

Therefore, when the elapsed time since the display of the manualregeneration warning exceeds the reference time t1 (but not thereference time t2), the speaker 6 c outputs a first warning sound (e.g.,three, short, low-volume beep sounds). When the operator notices thefirst warning sound and turns on the regeneration switch 38,regeneration control is started (the process flows from S12 to S23, toS24, to S25, to S26, to S13, and to S14).

However, because the excavator's work may often coincide with otherconstruction work at the construction site, the noise may prevent theoperator from noticing the first warning sound. Thus, when the elapsedtime since the display of the manual regeneration warning exceeds thereference time t2 (but not the reference time t3), the speaker 6 cinstead outputs a second warning sound (e.g., five, long, medium-volume,low-pitched beep sounds). When the operator notices the second warningsound and turns on the regeneration switch 38, regeneration control isstarted (the process flows from S25 to S26, to S27, to S28, to S13, andto S14).

If manual regeneration is not performed after the second warning sound,it is prompted with a louder sound. When the elapsed time since thedisplay of the manual regeneration warning exceeds the reference timet3, the speaker 6 c instead outputs a third warning sound (e.g., acontinuous, large-volume, lower-pitched beep sound). When the operatornotices the third warning sound and turns on the regeneration switch 38,regeneration control is started (the process flows from S25 to S26, toS27, to S28, to S13, and to S14).

If manual regeneration is not performed after the third warning soundand a particular amount of time has passed since the third warningsound, regeneration is prohibited. This is because an excessive amountof accumulated particulate matter may burn abruptly, increasing thefilter temperature excessively and damaging the filter.

The above basic operation of the exhaust purification system is based onthe assumption that the hydraulic excavator is in work-in-progressstatus. When the excavator is judged to be in work-in-progress status,the reference times t1, t2, and t3 for work-in-progress status are set(S21 to S22).

(2) Next described is the operation of the exhaust purification systemwhen the excavator is put on standby.

One of the tasks of the hydraulic excavator is to load excavated soilonto dump trucks. The soil is often gathered at a single location forthe excavator to load it onto waiting dump trucks. The dump trucks areused to transport the soil to another location. When the dump trucks aresmall in number, the excavator has to wait longer for a next dump tocome.

When the hydraulic excavator is in standby status, the exhausttemperature decreases drastically. Thus, self-regeneration and automaticregeneration may not be performed properly, resulting in furtheraccumulation of particulate matter compared with work-in-progressstatus.

Accordingly, when the excavator is judged to be in standby status, thereference times t1, t2, and t3 for standby status are set (S21 to S22).The reference times t1, t2, and t3 for standby status are shorter thanthe reference times t1, t2, and t3 for work-in-progress status,respectively. This means that the first, second, and third warningsounds output during standby status are output earlier than those outputduring work-in-progress status. When the operator notices one of thewarning sounds and turns on the regeneration switch 38, regenerationcontrol is started.

(3) When the engine 1 is halted during the output of any of the warningsounds, all control is halted as well. In that case, the elapsed timemeasured thus far is stored on the memory 41 c. When the key switch 5 isoperated again to start the supply of power to the controller 4, thedisplay device 6, and so forth, the elapsed time stored last will beread from the memory 41 c, and a warning sound is also output before thestart-up of the engine 1.

Advantages

(1) When the elapsed time since the display of a manual regenerationwarning is short and the DPF device is less likely to be damaged (thanin the cases described below), the first warning sound, or a low-volumebeep sound, is output. Since the volume of the first warning sound islow, the operator will not find it annoying. By the operator noticingthe first warning sound and performing proper manual regeneration,damage to the DPF device can be avoided.

When manual regeneration is not performed after the output of the firstwarning sound and the elapsed time becomes longer, the DPF device ismore likely to be damaged. In that case, the speaker 6 c outputs thesecond warning sound (louder than the first) and the third warning sound(louder than the second). Since the second and third warning sounds arelouder beep sounds, the operator will notice them easily. By theoperator then performing proper manual regeneration, damage to the DPFdevice can be avoided.

(2) In conventional techniques, the content of a warning is changedbased on an estimated amount of accumulated PM. Thus, if the estimatehas errors, the warning may not be changed properly. Especially, whenthe estimate is smaller than the actual amount and a warning is changedbased on that estimate, judgment associated with the alteration of thewarning may be delayed. This delay could be an indirect cause of DPFbreakage because manual regeneration cannot be performed properly (i.e.,the start of the manual regeneration is delayed).

In the present embodiment, by contrast, warning sounds are changed basedon elapsed time. This allows the warning sounds to be changed morereliably without being affected by PM estimation errors, and by theoperator noticing the warning sounds and performing manual regeneration,damage to the DPF device can be avoided.

(3) While the hydraulic excavator is designed to do excavation work andits work-in-progress status often lasts a long period of time, it mayoccasionally be put on standby for a long time depending on the work.During standby status, more particulate matter may be accumulated thanduring work-in-progress status. Thus, changing warning sounds based onthe reference times for work-in-progress status may delay judgmentassociated with the alteration of the warning sounds.

Therefore, in the present embodiment, warning sounds are changed basedon the reference times for standby status while the excavator is put onstandby. This allows the warning sounds to be changed more reliablywithout the associated judgment being delayed. In that case as well, bythe operator noticing the warning sounds and performing manualregeneration, damage to the DPF device can be avoided.

Modifications

(1) The present embodiment uses three warning sounds: the first warningsound (e.g., three, short, low-volume, midrange beep sounds), the secondwarning sound (e.g., five, long, medium-volume, low-pitched beepsounds), and the third warning sound (e.g., a continuous, large-volume,lower-pitched beep sound). The first warning sound is changed to thesecond warning sound, and the second warning sound is changed to thethird warning sound. Note however that this is meant to be an example,and the volume, tone, length, or number of the warning sounds can bechanged as desired.

(2) While, in the present embodiment, a warning message prompting manualregeneration is displayed (Step S12) based on the PM amount estimated bythe differential pressure detector 36, it can instead be based on theelapsed time since the start of excavation work so that PM estimationerrors will not affect the timing of the warning display.

(3) While, in the present embodiment, the warning sounds are changedbased on the elapsed time since the display of a warning message, theycan instead be changed based on an estimated PM amount if the estimateis highly accurate.

(4) While, in the present embodiment, the warning sounds are changedbased the elapsed time, it is also possible to change a warning messagedisplayed on the screen 6 a into ones attracting more attention.

Embodiment 2 Problem Associated With Embodiment 1

Described below is the operation of the exhaust purification system ofEmbodiment 1 when the excavator is shifted from standby status back towork-in-progress status during the control by the system. During standbystatus, more particulate matter is accumulated than duringwork-in-progress status. Assume that the excavator is shifted back towork-in-progress status and that the reference times t1, t2, and t3 forwork-in-progress status are set again. In that case, using the referencetimes t1, t2, and t3 for work-in-progress status based on the elapsedtime measured during standby status results in the alteration of warningsounds being delayed.

This is discussed in greater detail with reference to FIG. 6. FIG. 6 isa graph illustrating the problem resulting from the different referencetimes set for standby status and work-in-progress status. The horizontalaxis represents time while the vertical axis represents the amount ofaccumulated PM. The threshold Q represents the accumulated PM amount atwhich warning sounds should be changed, and the reference time T forwork-in-progress status represents the time at which warning soundsshould be changed during work-in-progress status. The lower solid linerepresents the accumulation of PM during work-in-progress status. Duringstandby status, particulate matter is assumed to be accumulated X timesas much as during work-in-progress status (X being a positive numbergreater than 1). The upper solid line represents the accumulation of PMduring standby status. Thus, the reference time T/X for standby status(i.e., the time at which the threshold Q is reached during standbystatus) is calculated by multiplying the reference time T forwork-in-progress status by the reciprocal of X (i.e., 1/X).

The dotted line represents the accumulation of PM when the excavator isshifted from standby status to work-in-progress status at Point A. Whenthe excavator is judged to be in work-in-progress status at Point A, thereference time T for work-in-progress status is set again. However, thePM amount reaches the threshold Q at Point B before the measured timereaches the reference time T for work-in-progress status. This meansthat changing warning sounds after the reference time T forwork-in-progress status has been reached is too late.

Configuration and Advantages of Embodiment 2

In Embodiment 2, the warning sound altering function 41 b of Embodiment1 is allowed to have an elapsed-time converting function 41 d (see FIG.4).

FIG. 7 is a graph illustrating how the elapsed-time converting function41 d works. Similar to FIG. 6, FIG. 7 illustrates a case where theexcavator is shifted from standby status to work-in-progress status atPoint A, and the elapsed time at Point A is denoted by t.

The elapsed-time converting function 41 d calculates Point C on the linethat represents the PM accumulation during work-in-progress status suchthat it becomes equal to the PM amount at Point A. In FIG. 7, theconverted elapsed time at Point C is denoted by Xt. The convertedelapsed time Xt is obtained by assuming that the excavator has been inwork-in-progress status.

When the elapsed time measured is t, the warning sound altering function41 b coverts the time t into the converted elapsed time Xt, followed bythe continuation of time measurement from the time Xt. When the elapsedtime reaches the reference time T for work-in-progress status (i.e., thetime at which the threshold Q is reached), warning sounds are changed.

The elapsed-time converting function 41 d of Embodiment 2 preventswarning sound alteration judgment from being delayed when the excavatoris shifted from standby status back to work-in-progress status, thusensuring a reliable alternation of warning sounds. By the operatornoticing the warning sounds and performing manual regeneration properly,damage to the DPF device can be avoided.

If, on the other hand, the excavator is shifted from work-in-progressstatus back to standby status, the elapsed-time converting function 41 dinstead calculates converted elapsed time t/X when the elapsed timemeasured is t.

DESCRIPTION OF REFERENCE NUMERALS

1: Diesel engine

1 a: Electronic governor

2: Engine control dial

3: Speed detector

4: Controller

5: Key switch

6: Display device

6 a: Screen

6 b: Control switch

6 c: Speaker

7: Gate lock lever

8: Position detector

11: Hydraulic pump

12: Pilot pump

13: Hydraulic motor

14, 15: Hydraulic cylinder

17 to 19: Flow-rate control valve

20: Pilot hydraulic pressure source

21: Pilot relief valve

22: Main relief valve

23: Solenoid valve

24: Pilot hydraulic line

25, 26, 27: Remote control valve

28, 29: Operating lever

31: Exhaust pipe

32: Filter

33: Oxidation catalyst

34: DPF device

36: Differential pressure detector

37: Exhaust temperature detector

38: Regeneration switch

39: Fuel injector

41: Vehicle controller

41 a: Status judgment function

41 b: Warning sound altering function

41 c: Memory

41 d: Elapsed-time converting function (Embodiment 2)

42: Engine controller

42 a: Manual regeneration function

43: Display controller

44: Communication line

46: Shuttle valve

47: Pressure sensor

100: Lower carrier structure

102: Front shovel structure

103 a, 103 b: Crawler belt

104 a, 104 b: Travel motor

105: Swing motor

106: Engine room

107: Cab

108: Cab seat

111: Boom

112: Arm

113: Bucket

114: Boom cylinder

115: Arm cylinder

116: Bucket cylinder

1. (canceled)
 2. (canceled)
 3. An exhaust purification system forworking machine, the system comprising: a filler (32), located in anexhaust system of an engine (1), for capturing particulate mattercontained in exhaust; a regeneration device (33, 39) for burning offparticulate matter accumulated on the filter to regenerate the filler; aregeneration controller (42) for starting or stopping the operation ofthe regeneration device; a regeneration switch (38) for instructing theregeneration controller to start regeneration; and warning means (6 a,42 a, 43) for prompting an operator to turn on the regeneration switch,wherein the system further comprises status judging means (3, 8, 41 a,47) for judging the status of the working machine, wherein the warningmeans includes a warning sound output function (6 c) for outputtingwarning sounds and a warning sound altering function (41 b) for alteringthe warning sounds after the amount of time during which the statusjudging means judges the working machine to be in operation has exceededreference times since a first warning, wherein in the event that thestatus judging means judges the working machine to be in operation, thestatus judging means further judges whether the working machine is instandby status or work-in-progress status, and wherein the warning soundaltering function sets different reference times depending on thestandby status or the work-in-progress status.
 4. The exhaustpurification system of claim 3 wherein the working machine comprises: anengine speed detector (3); a work-performing structure; operating levers(28, 29) for controlling the operation of the work-performing structure;a gate lock lever (7) movable between an unlock position that enablesthe operation of the operating levers and a lock position that disablesthe operation of the operating levers; and a pilot pressure sensor (47)for detecting pilot pressures generated by the operating levers, whereinthe status judging means judges the working machine to be in the standbystatus in the event that the engine speed detector has detected a speedhigher than a low idle speed and that the gate lock lever is in the lockposition, and wherein the status judging means judges the workingmachine to be in the work-in-progress status in the event that theengine speed detector has detected a speed higher than the low idlespeed, that the gate lock lever is in the unlock position, and that thepilot pressure sensor has detected a pressure higher than a given value.5. The exhaust purification system of claim 3 wherein the warning soundaltering function alters at least either one of the following: thevolume, tone, length, and repeat count of the warning sounds. 6.(canceled)